Internet Engineering Task Force (IETF) S. Gundavelli, Ed.
Request for Comments: 6757 Cisco
Category: Standards Track J. Korhonen, Ed.
ISSN: 2070-1721 Nokia Siemens Networks
M. Grayson
K. Leung
R. Pazhyannur
Cisco
October 2012
Access Network Identifier (ANI) Option for Proxy Mobile IPv6
Abstract
The local mobility anchor in a Proxy Mobile IPv6 (PMIPv6) domain is
able to provide access-network- and access-operator-specific handling
or policing of the mobile node traffic using information about the
access network to which the mobile node is attached. This
specification defines a mechanism and a related mobility option for
carrying the access network identifier and the access operator
identification information from the mobile access gateway to the
local mobility anchor over Proxy Mobile IPv6.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6757.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
Gundavelli, et al. Standards Track [Page 1]

RFC 6757 Access Network Identifier Option October 20121. Introduction
Proxy Mobile IPv6 [RFC5213] can be used for supporting network-based
mobility management in various types of network deployments. Network
architectures such as service provider Wi-Fi access aggregation or
Wireless Local Area Network (WLAN) integrated with mobile packet core
are examples where Proxy Mobile IPv6 is a component of the overall
architecture. Some of these architectures require the ability of the
local mobility anchor (LMA) [RFC5213] to provide differentiated
services and policing of traffic to the mobile nodes based on the
access network to which they are attached. Policy systems in
mobility architectures such as the Policy and Charging Control (PCC)
Framework [TS23203] and the Access Network Discovery and Selection
Function (ANDSF) [TS23402] in Third Generation Partnership Project
(3GPP) systems allow configuration of policy rules with conditions
based on the access network information. For example, the service
treatment for the mobile node's traffic may be different when it is
attached to an access network owned by the home operator than when
owned by a roaming partner. The service treatment can also be
different based on the configured Service Set Identifiers (SSIDs) in
the case of access networks based on IEEE 802.11. Other examples of
location services include the operator's ability to display a
location-specific web page or apply tariff based on the location.
The Proxy Mobile IPv6 specification [RFC5213] requires the Access
Technology Type (ATT) option to be carried from the mobile access
gateway (MAG) to the local mobility anchor. This is a mandatory
option. However, the Access Technology Type alone is not necessarily
sufficient for a suitable policy to be applied at the local mobility
anchor. Therefore, there is a need for additional access-network-
related information to be available at the local mobility anchor.
Learning the identity of the access network operator may not be
possible for a local mobility anchor without the support of an
additional policy framework that is able to provide required
information out of band to the local mobility anchor. Such a policy
framework may not be required for all Proxy Mobile IPv6 deployments;
hence, an alternative approach for optionally carrying such
information is required to ensure that additional information related
to the access network is available.
This document defines a new mobility option, the Access Network
Identifier (ANI) option, and its sub-options for Proxy Mobile IPv6,
which can be used by the mobile access gateway to signal the access
network information to the local mobility anchor. The specific
details on how the local mobility anchor uses the information
contained in the Access Network Identifier option are out of scope
for this document. This information is intended for use between
infrastructure nodes providing mobile management service and is not
Gundavelli, et al. Standards Track [Page 3]

RFC 6757 Access Network Identifier Option October 2012
exposed to outside entities, which ensures the location of the
network to which the mobile node is attached, or any other access-
network-specific information, is not revealed to other mobile nodes
within the PMIPv6 domain or to other nodes outside the PMIPv6 domain.
However, the location and access information MAY be exposed to
specific parties outside the PMIPv6 domain based on an agreement
approved by the subscriber; otherwise, this information MUST NOT be
exposed in the absence of such agreements. If the location
information is to be exposed outside the PMIPv6 domain, then that
MUST be done using a Presence Information Data Format Location Object
(PIDF-LO) [RFC5139] carrying the usage rules to which the subscriber
has agreed. This mobility option is optional and is not mandatory
for the Proxy Mobile IPv6 protocol. However, the Access Technology
Type option continues to be a mandatory option and always needs to be
carried in the Proxy Mobile IPv6 signaling messages.
SSID: IETF-1
Geo-Location: 37o49'11"N 122o28'43"W
Operator-Identifier: provider1.example.com
+--+
|AP|-------. {Access-Specific Policies)
+--+ | _-----_ |
+-----+ _( )_ +-----+
| MAG |-=====( PMIPv6 )======-| LMA |-
+-----+ (_ Tunnel_) +-----+
+--+ | '-----'
|AP|-------'
+--+
SSID: IETF-2
Geo-Location: 59o19'40.21"N 18o 3'18.36"E
Operator-Identifier: provider2.example.com
Figure 1: Access Networks Attached to MAG
Figure 1 illustrates an example Proxy Mobile IPv6 deployment where
the mobile access gateway delivers the information elements related
to the access network to the local mobility anchor over Proxy Mobile
IPv6 signaling messages. In this example, the additional information
could comprise the SSID of the used IEEE 802.11 network, the geo-
location of the network to which the mobile node is attached, and the
identities of the operators running the IEEE 802.11 access network
infrastructure.
Gundavelli, et al. Standards Track [Page 4]

RFC 6757 Access Network Identifier Option October 20122. Conventions and Terminology2.1. Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
2.2. Terminology
All the mobility-related terms used in this document are to be
interpreted as defined in the Proxy Mobile IPv6 specifications
[RFC5213] and [RFC5844]. Additionally, this document uses the
following abbreviations:
Service Set Identifier
Service Set Identifier (SSID) identifies the name of the IEEE
802.11 network. SSID differentiates one network from the other.
Operator-Identifier
The Operator-Identifier is the Structure of Management Information
(SMI) Network Management Private Enterprise Code of the IANA-
maintained "Private Enterprise Numbers" registry [SMI]. It
identifies the operator running the network attached to a specific
interface of the mobile access gateway.
3. Access Network Identifier Option
The Access Network Identifier option is a mobility header option used
to exchange information related to the access network between a local
mobility anchor and a mobile access gateway. The option can be
included in both Proxy Binding Update (PBU) and Proxy Binding
Acknowledgement (PBA) messages, and there MUST NOT be more than a
single instance of this mobility option in a mobility message. The
Access Network Identifier mobility option MUST contain one or more
Access Network Identifier sub-options. The Access Network Identifier
sub-option is described in Section 3.1.
Gundavelli, et al. Standards Track [Page 5]

RFC 6757 Access Network Identifier Option October 2012
ANI Length: 8-bit unsigned integer indicating the number of octets
needed to encode the Option Data, excluding the ANI Type and ANI
Length fields of the sub-option.
3.1.1. Network-Identifier Sub-Option
The Network-Identifier is a mobility sub-option carried in the Access
Network Identifier option defined in Section 3. This sub-option
carries the name of the access network (e.g., an SSID in the case of
an IEEE 802.11 Access Network or a Public Land-based Mobile Network
(PLMN) Identifier [TS23003] in the case of 3GPP access) to which the
mobile node is attached. There MUST be no more than a single
instance of this specific sub-option in any Access Network Identifier
option. The format of this option is defined below.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ANI Type=1 | ANI Length |E| Reserved | Net-Name Len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Network Name (e.g., SSID or PLMNID) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AP-Name Len | Access-Point Name ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Network-Identifier Sub-Option
ANI Type: MUST be set to the value of (1), indicating that it is a
Network-Identifier sub-option
ANI Length: Total length of this sub-option in octets, excluding the
ANI Type and ANI Length fields. The value can be in the range of
5 to 32 octets.
E: 1-bit flag indicating whether the Network Name is encoded in
UTF-8. If this flag is set to one (1), then the Network Name is
encoded using UTF-8 [RFC3629]. If the flag is set to zero (0),
this indicates that the encoding is undefined and is determined by
out-of-band mechanisms. Implementations SHOULD use UTF-8
encoding.
Reserved: MUST be set to zero when sending and ignored when
received.
Net-Name Length: 8-bit field for representing the length of the
Network Name in octets. This field MUST NOT be set to zero.
Gundavelli, et al. Standards Track [Page 7]

RFC 6757 Access Network Identifier Option October 2012
Network Name: The name of the access network to which the mobile
node is attached. The type of the Network Name is dependent on
the access technology to which the mobile node is attached. If it
is 802.11 access, the Network Name MUST be the SSID of the
network. If the access network is 3GPP access, the Network Name
is the PLMN Identifier of the network. If the access network is
3GPP2 access, the Network Name is the Access Network Identifier
[ANI].
When encoding the PLMN Identifier, both the Mobile Network Code
(MNC) [TS23003] and Mobile Country Code (MCC) [TS23003] MUST be 3
digits. If the MNC in use only has 2 digits, then it MUST be
preceded with a '0'. Encoding MUST be UTF-8.
AP-Name Len: 8-bit field for representing the length of the Access-
Point Name in octets. If the Access-Point Name is not included,
then this length MUST be set to a value of zero.
Access-Point Name: The name of the access point (physical device
name) to which the mobile node is attached. This is the
identifier that uniquely identifies the access point. While
Network Name (e.g., SSID) identifies the operator's access
network, Access-Point Name identifies a specific network device in
the network to which the mobile node is attached. In some
deployments, the Access-Point Name can be set to the Media Access
Control (MAC) address of the device or some unique identifier that
can be used by the policy systems in the operator network to
unambiguously identify the device. The string is carried in UTF-8
representation.
3.1.2. Geo-Location Sub-Option
The Geo-Location is a mobility sub-option carried in the Access
Network Identifier option defined in Section 3. This sub-option
carries the geo-location of the network to which the mobile node is
attached, as known to the mobile access gateway. There MUST be no
more than a single instance of this specific sub-option in any Access
Network Identifier option. The format of this option is defined
below and encodes the coordinates of an ellipsoid point. The format
is based on the coordinate reference system specified in the World
Geodetic System 1984 [WGS84].
Gundavelli, et al. Standards Track [Page 8]

RFC 6757 Access Network Identifier Option October 2012
ANI Type: It MUST be set to the value of (3), indicating that it is
the Operator-Identifier sub-option
ANI Length: Total length of this sub-option in octets, excluding the
ANI Type and ANI Length fields.
Operator-Identifier (Op-ID) Type: 8-bit unsigned integer indicating
the type of the Operator-Identifier. Currently, the following
types are defined:
0 - Reserved.
1 - Operator-Identifier as a variable-length Private Enterprise
Number (PEN) [SMI] encoded in a network-byte order. The
maximum PEN value depends on the ANI Length and is calculated
using the formula: maximum PEN = 2^((ANI_length-1)*8)-1. For
example, the ANI Length of 4 allows for encoding PENs from 0
to 2^24-1, i.e., from 0 to 16777215, and uses 3 octets of
Operator-Identifier space.
2 - Realm of the operator. Realm names are required to be unique
and are piggybacked on the administration of the DNS
namespace. Realms meet the syntactic requirements of the
"Preferred Name Syntax" defined in Section 2.3.1 of
[RFC1035]. They are encoded as US-ASCII. 3GPP specifications
also define realm names that can be used to convey PLMN
Identifiers [TS23003].
Operator-Identifier: Up to 253 octets of the Operator-Identifier.
The encoding of the identifier depends on the used Operator-
Identifier Type. For Operator-Identifiers defined in this
specification, the Operator-Identifier MUST NOT be empty.
4. Protocol Considerations
The following considerations apply to the local mobility anchor and
the mobile access gateway.
4.1. Mobile Access Gateway Considerations
o The conceptual Binding Update List entry data structure maintained
by the mobile access gateway, described in Section 6.1 of
[RFC5213], MUST be extended to store the access-network-related
information elements associated with the current session.
Specifically, the following parameters MUST be defined:
Gundavelli, et al. Standards Track [Page 10]

RFC 6757 Access Network Identifier Option October 2012
Network-Identifier
Operator-Identifier
Geo-Location
o If the mobile access gateway is configured to support the Access
Network Information option, it SHOULD include this option with the
specific sub-options in all Proxy Binding Update messages
(including Proxy Binding Updates for lifetime extension and for
deregistration) that it sends to the local mobility anchor. The
Access Network Information option MUST be constructed as specified
in Section 3. It SHOULD include the ANI sub-option(s) that the
mobile access gateway is configured to carry in the Proxy Mobile
IPv6 messages.
o The access network information elements, such as Network-
Identifier, Geo-Location, and Operator-Identifier, typically are
statically configured on the mobile access gateway on a per-
interface basis (for example, access point (AP-1) is attached
through interface-1, and the SSID is X, Geo-Location is Y). In
some deployments, this information can also be dynamically
obtained, such as through DHCP Option (82), which is the DHCP
Relay Agent Information option [RFC3046]. When the mobile node
sends a DHCP Request, the access points typically add the SSID
information to the Option 82 of the DHCP request, and when the
mobile access gateway receives this request, it can parse the
Option 82 of the DHCP request and obtain the SSID name. The
mobility access gateway can also obtain this information from the
DHCPv6 GeoLoc Option [RFC6225]. The specific details on how the
mobile access gateway obtains these information elements are
access technology and deployment specific and are outside the
scope of this document. It is possible those information elements
are configured on the MAG on a per-interface basis or dynamically
obtained through some out-of-band means, such as based on the
Control and Provisioning of Wireless Access Points (CAPWAP)
protocol.
o If the protocol configuration variable
EnableANISubOptNetworkIdentifier (Section 6) is set to a value of
(1), the mobile access gateway SHOULD include the Network-
Identifier sub-option in the Access Network Identifier option
carried in the Proxy Binding Update. However, if the mobile
access gateway is unable to obtain the Network-Identifier, then it
MUST NOT include this sub-option. For including the Network-
Identifier sub-option, the mobile access gateway needs to be aware
of the Network Name of the access network (e.g., SSID in the case
of a WLAN access network) to which the mobile node is attached.
Gundavelli, et al. Standards Track [Page 11]

RFC 6757 Access Network Identifier Option October 2012
This sub-option also includes the Access-Point Name for carrying
the name of the access point to which the mobile node is attached.
The Access-Point Name is specially important for applying location
services, given that the Network Name (e.g., SSID) may not provide
the needed uniqueness for identifying a location. When included,
this sub-option MUST be constructed as described in Section 3.1.1
o If the protocol configuration variable EnableANISubOptGeoLocation
(Section 6) is set to a value of (1), the mobile access gateway
SHOULD include the Geo-Location sub-option in the Access Network
Identifier option carried in the Proxy Binding Update. However,
if the mobile access gateway is unable to obtain the Geo-location,
then it MUST NOT include this sub-option. For including the Geo-
Location sub-option, the mobile access gateway needs to be aware
of the GPS coordinates of the network to which the mobile node is
attached. When included, this sub-option MUST be constructed as
described in Section 3.1.2.
o If the protocol configuration variable
EnableANISubOptOperatorIdentifier (Section 6) is set to a value of
(1), the mobile access gateway SHOULD include the Operator-
Identifier sub-option in the Access Network Identifier option
carried in the Proxy Binding Update. For including the Operator-
Identifier sub-option, the mobile access gateway needs to be aware
of the operator identity of that access network. The access
network operator SHOULD obtain an identifier from the "Private
Enterprise Number" registry, in order for the mobile access
gateway to carry the Operator-Identifier. If a given access
network operator has not obtained an identifier from the "Private
Enterprise Number" registry or if the mobile access gateway is
unable to learn the operator identity for any other administrative
reasons, then it MUST NOT include this sub-option. When included,
this sub-option MUST be constructed as described in Section 3.1.3.
If the mobile access gateway had any of the Access Network
Information mobility options included the Proxy Binding Update sent
to a local mobility anchor, then the Proxy Binding Acknowledgement
received from the local mobility anchor SHOULD contain the Access
Network Information mobility option with the specific sub-options.
If the mobile access gateway receives a Proxy Binding Acknowledgement
with a successful Status Value but without an Access Network
Information mobility option, then the mobile access gateway SHOULD
log the event and, based on its local policy, MAY proceed to
terminate the mobility session. In this case, the mobile access
gateway knows the local mobility anchor does not understand the
Access Network Information mobility option and therefore MAY consider
it as a misconfiguration of the Proxy Mobile IPv6 domain.
Gundavelli, et al. Standards Track [Page 12]

RFC 6757 Access Network Identifier Option October 20124.2. Local Mobility Anchor Considerations
o The conceptual Binding Cache entry data structure maintained by
the local mobility anchor, described in Section 5.1 of [RFC5213],
MUST be extended to store the access-network-related information
elements associated with the current session. Specifically, the
following parameters MUST be defined:
Network-Identifier
Geo-Location
Operator-Identifier
o On receiving a Proxy Binding Update message [RFC5213] from a
mobile access gateway with the Access Network Information option,
the local mobility anchor must process the option and update the
corresponding fields in the Binding Cache entry. If the option is
not understood by that LMA implementation, it will skip the
option.
o If the local mobility anchor understands the Access Network
Identifier mobility option received in a Proxy Binding Update and
also supports the sub-option(s), then the local mobility anchor
MUST echo the Access Network Identifier mobility option with the
specific sub-option(s) that it accepted back to the mobile access
gateway in a Proxy Binding Acknowledgement. The Access Network
Identifier sub-options defined in this specification MUST NOT be
altered by the local mobility anchor.
o If the received Proxy Binding Update message does not include the
Access Network Information option, then the mobility session
associated with that Proxy Binding Update MUST be updated to
remove any access network information elements.
o The local mobility anchor MAY choose to use the Access Network
Information sub-options for applying any access-operator-specific
handling or policing of the mobile node traffic. The specific
details on how these sub-options are used is outside the scope of
this document.
Gundavelli, et al. Standards Track [Page 13]

RFC 6757 Access Network Identifier Option October 20125. IANA Considerations
Per this document, the following IANA actions have been completed.
o Action 1: This specification defines a new mobility header option,
the Access Network Identifier. This mobility option is described
in Section 3. The type value (52) for this option has been
assigned from the same numbering space as allocated for the other
mobility options, as defined in [RFC6275].
o Action 2: This specification defines a new mobility sub-option
format, the Access Network Information (ANI) sub-option. The
format of this mobility sub-option is described in Section 3.1.
This sub-option can be carried in the Access Network Information
option. The type value for this sub-option is managed by IANA,
under the registry "Access Network Information (ANI) Sub-Option
Type Values". This specification reserves the following type
values. Approval of new Access Network Information (ANI) sub-
option type values are to be made through IANA Expert Review.
+=========================================================+
| 0 | Reserved |
+=========================================================+
| 1 | Network-Identifier sub-option |
+=========================================================+
| 2 | Geo-Location sub-option |
+=========================================================+
| 3 | Operator-Identifier sub-option |
+=========================================================+
o Action 3: This specification defines a new mobility sub-option,
the Operator-Identifier sub-option. The format of this mobility
sub-option is described in Section 3.1.3. The Operator-Identifier
(Op-ID) Type field of this sub-option introduces a new number
space. This number space is managed by IANA, under the registry
"Operator-Identifier Type Registry". This specification reserves
the following type values. Approval of new Operator-Identifier
type values are to be made through IANA Expert Review.
+===============================================+
| 0 | Reserved |
+===+===========================================+
| 1 | Operator-Identifier as a variable-length |
| | Private Enterprise Number (PEN) |
+===+===========================================+
| 2 | Realm of the Operator |
+===+===========================================+
Gundavelli, et al. Standards Track [Page 14]

RFC 6757 Access Network Identifier Option October 20126. Protocol Configuration Variables
This specification defines the following configuration variables that
control the use of sub-options related to the Access Network
Information in Proxy Mobile IPv6 signaling messages. The mobility
entities, local mobility anchor, and mobile access gateway MUST allow
these variables to be configured by the system management. The
configured values for these protocol variables MUST survive server
reboots and service restarts.
EnableANISubOptNetworkIdentifier
This flag indicates the operational state of the Network-
Identifier sub-option support. This configuration variable is
available at both the mobile access gateway and the local mobility
anchor. The default value for this flag is set to (0), indicating
that support for the Network-Identifier sub-option is disabled.
When this flag on the mobile access gateway is set to a value of
(1), the mobile access gateway SHOULD include this sub-option in
the Proxy Binding Update messages that it sends to the local
mobility anchor; otherwise, it SHOULD NOT include the sub-option.
There can be situations where the mobile access gateway is unable
to obtain the Network-Identifier and may not be able to construct
this sub-option.
Similarly, when this flag on the local mobility anchor is set to a
value of (1), the local mobility anchor SHOULD enable support for
this sub-option; otherwise, it SHOULD ignore this sub-option.
EnableANISubOptGeoLocation
This flag indicates the operational state of the Geo-Location sub-
option support. This configuration variable is available at both
the mobile access gateway and the local mobility anchor. The
default value for this flag is set to (0), indicating that support
for the Geo-Location sub-option is disabled.
When this flag on the mobile access gateway is set to a value of
(1), the mobile access gateway SHOULD include this sub-option in
the Proxy Binding Update messages that it sends to the local
mobility anchor; otherwise, it SHOULD NOT include the sub-option.
There can be situations where the mobile access gateway is unable
to obtain the geo-location information and may not be able to
construct this sub-option.
Gundavelli, et al. Standards Track [Page 15]

RFC 6757 Access Network Identifier Option October 2012
Similarly, when this flag on the local mobility anchor is set to a
value of (1), the local mobility anchor SHOULD enable support for
this sub-option; otherwise, it SHOULD ignore this sub-option.
EnableANISubOptOperatorIdentifier
This flag indicates the operational state of the Operator-
Identifier sub-option support. This configuration variable is
available at both the mobile access gateway and the local mobility
anchor. The default value for this flag is set to (0), indicating
that support for the Operator-Identifier sub-option is disabled.
When this flag on the mobile access gateway is set to a value of
(1), the mobile access gateway SHOULD include this sub-option in
the Proxy Binding Update messages that it sends to the local
mobility anchor; otherwise, it SHOULD NOT include the sub-option.
There can be situations where the mobile access gateway is unable
to obtain the Operator-Identifier information and may not be able
to construct this sub-option.
Similarly, when this flag on the local mobility anchor is set to a
value of (1), the local mobility anchor SHOULD enable support for
this sub-option; otherwise, it SHOULD ignore this sub-option.
7. Security Considerations
The Access Network Information option defined in this specification
is for use in Proxy Binding Update and Proxy Binding Acknowledgement
messages. This option is carried like any other mobility header
option as specified in [RFC6275] and does not require any special
security considerations.
The Geo-Location sub-option carried in the Access Network Information
option exposes the geo-location of the network to which the mobile
node is attached. This information is considered to be very
sensitive, so care must be taken to secure the Proxy Mobile IPv6
signaling messages when carrying this sub-option. The base Proxy
Mobile IPv6 specification [RFC5213] specifies the use of IPsec for
securing the signaling messages, and those mechanisms can be enabled
for protecting this information. Operators can potentially apply
IPsec Encapsulating Security Payload (ESP) with confidentiality and
integrity protection for protecting the location information.
Access-network-specific information elements that the mobile access
gateway sends may have been dynamically learned over DHCP or using
other protocols. If proper security mechanisms are not in place, the
exchanged information may be potentially compromised with the mobile
access gateway sending incorrect access network parameters to the
Gundavelli, et al. Standards Track [Page 16]